Technical Field
The present technology relates to a pneumatic tire in which plurality of polygonal blocks is disposed in a tread portion, and particularly relates to a pneumatic tire whereby braking performance on wet road surfaces and steering stability on dry road surfaces can be improved in a well-balanced manner.
Related Art
Conventionally, in pneumatic tires, a plurality of circumferential grooves extending in a tire circumferential direction and a plurality of lateral grooves extending in a tire width direction are formed in a tread portion, and multiple blocks are partitioned by these circumferential grooves and lateral grooves (e.g. see Japanese Unexamined Patent Application Publication No. 2010-83462A and Japanese Unexamined Patent Application Publication No. 2011-25864A). Additionally, sipes are formed in the blocks as necessary. In such a pneumatic tire, increasing the number of grooves and/or sipes in order to enhance water drainage performance and increase edge effect is effective for enhancing braking performance on wet road surfaces.
However, there is a problem in that when the number of grooves and/or sipes disposed in the tread portion is simply increased, rigidity of the tread portion decreases and steering stability on dry road surfaces declines. Additionally, investigation into narrowing the grooves in order to suppress the decline in the rigidity of the tread portion has been carried out. However, in cases where the grooves are narrowed, water drainage effects are insufficient. Moreover, in cases where the grooves have been narrowed and the number thereof increased, rigidity of the tread portion decreases. Therefore, it is difficult to achieve both braking performance on wet road surfaces and steering stability on dry road surfaces.